#include<stdio.h>
#include<math.h>
int main()
{//97 8 17
int h;
	double r,v;
	scanf("%d %lf %lf",&h,&r,&v);
	if(v==0)
	{
	    printf("%d",h);
	    return 0;
	}
	if(r==0)
	{
	    printf("0");
	    return 0;
	}
    double a;
    a=v/r;
    
	
    a=ceil(a);
    
    h=h-(int)a;
    if(h<0)
    {
        printf("0");
        return 0;
    }
    printf("%d\n",h);
	return 0;
}